Heating and rolling steel



Patented May 27, 1941 HEATING AND ROLLING STEEL Arthur-B. Bixby, Cleveland Heights, Ohio, assignor to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey No Drawing. LApplication April 28, 1939, Serial No. 270,649

4 Claims.

. when the oxidized metal and scale is removed,

pits, depressions or defects are formed in the surfaces of the metal, particularly in the upper surface, which often are not entirely removed during hot rolling. When copper is present in the steel, and particularly when it is present in amounts from the neighborhood of about 50% and upwards to about 1.50%, the oxidation and scaling during heating also apparently reduces the amount of iron combined with the copper, thereby increasing the copper content in the surface portions ofthe slab. When such a slab is hot rolled, the rolled metal has a tendency to retain the pits and depressions traceable to oxidation and scaling, and also tends to become hardened and embrittled due to the increased amount of copper in the surface portions which, as just stated, is traceable to oxidation and removal of iron combined with copper with consequent copper enrichment.

The present invention aims to reduce the above described pitting troubles in rolled steel and also aims to prevent the hardening and embrittling action at present met with in the rolling of copper-containing steels.

The present invention is based on the discovery that if the slab is protected against oxidation and scaling during the time it is being heated to rolling temperature, as by a substance which covers the surface to be protected and which can either be removed from the steel prior to or during rolling, or will not be rolled into the steel, not only the pitting troubles but also the embrittling troubles above described may be reduced or substantially eliminated.

In carrying out the present process, a slab of steel is charged into the heating furnace and is provided with a quantity of such a material on its top surface. Preferably a substance which is solid at room temperature but which will melt ,at a temperature far below that of the furnace interior and will not volatilize at the furnace temperature is employed. Borax is an example of a substance which has been found to give good results in commercial use. stance, borax, for example, may be placed on the slab before or after the slab is charged into the furnace. It will melt almost immediately and will spread over the upper surface of the slab. A sufiicient amount of borax should be used so as to form a coating over the entire upper surface of the slab. The borax will. remain on the slab during the heating time, but when water is sprayed onto the metal during rolling, the borax will be removed by the water or with the scale. Even if not removed by, or as a result of, the water, the borax will not be rolled into the steel.

The protective substance prevents material amounts of oxidation and, in the case of copperbearing steels, prevents copper enrichment in the surface portion of the slab which it covers. While oxidation of the lower surface of the slab during heating and, in the case of a copperbearing steel, copper enrichment at the lower surface of the slab, takes place during heating of the slab to rolling temperature, neither the oxidation nor copper enrichment in the lower surface portions are ordinarily so extensive as to cause material difliculties. However, if desired, the lower surface of the slab may be protected against oxidation or copper enrichment by spraying a protective substance on, the lower surfaceof the slab or by heating the slab in a suitable receptacle, such as a shallow pan containing the substance.

The present invention has been described hereinabove in connection with the continuous rolling of steel. It will be obvious that it may also be applied with advantageous results to the noncontinuous rolling method. It will also be understood that its use is not confined to the rolling of slabs but that it may be used to advantage on smaller or larger pieces of metal regardless of the name by which they are commonly known in the industry. It will furtherbe understood that the invention is not confined to steels of any particular composition, but that it may be employed on steels of any composition where proatection of the surface of the steel against oxidation conditions is desired.

Having thus described the present invention so that-those skilled in the art may be able to practice the same, I state that what I desire to secure by Letters Patent is defined in what is claimed.

What isclaimed is:

1. The process of rolling steel which includes The protecting subtemperature in a slab heating furnace, protecting a surface of said slab of steel from oxidation and scaling throughout said heating operation by covering it with borax, removing said borax from the steel when the heating operation is completed, and rolling the steel.

3. The process of rolling 'steel which includes the steps of placing on a slab of steel to be heated and rolled a quantity of a solid substance which is non-volatile and liquid at steel rolling temperatures, heating the said steel in a slab heating furnace to a rolling temperature thereby melting said material and forming a thin layer thereof over a surface of the steel, removing said ma.- terial from said steel after the steel is removed from the iurnace, and rolling the steel.

4. The process of rolling steel which includes the steps 01' heating a slab of steel containing copper in amounts above about 50% to rolling temperature in a slab heating furnace, protecting the suriace of said steel from oxidation throughout said heating operation by covering it with a film of liquid borax, removing the borax after the heating operation is completed and before the steel is rolled, and rolling the steel.

- ARTHUR B. BIXBY. 

